Condition responsive, timing, and sequencing circuit control



A. WELLMAN April 24, 1951 Filed May 51, 1946 Z M 4 2 M M lw h 3 I W 71H5 ill Wi 4 m l Ilia a a 1 22. ,1 o E 2 B 0 I 2 I m 1 CRITICAL LOCKOUTPERIOD,

coouus PERIOD seas cwsso--1 HEATING PERIOD His Attorney.

Patented Apr. 24, 1951 CONDITION RESPONSIVE, TIMING, AND

IRCUIT CONTROL SEQUENCING 0 Albert Weilman, Scotia,

N. Y., assignor to General Electric Company, a corporation of New York IApplication May 31, 1946, Serial No. 673,338

13 Claims. lCl. 158-28) The invention relates to condition responsive,timing, and sequencing circuit control particularly of a type suitablefor the automaticcontrol of electrically operated oil burners or thelike.

7 One of the objects is to provide an improved form of multi-selectivecircuit control system capable of operating in response to differentpredetermined condition, time, and sequence control conditions toprovide timed starting and restarting, continued running, stopping, andsafety lockout of electrically operated oil burnersor the like.

. Another object is to minimize the essential automatic conditionresponsive, timing and sequencing switching elements involved by socombining, and interlocking their respective functions as to obtain amore eificient and less expensive form of multi-selective switching andsafety interlocking mechanism capable of insuring proper, reliable andsafe control of conventional electrically operated oil burners inautomatic domestic heating service under both normal and abnormalconditions.

Another object is to so combine a condition responsive reversely movableinterlocking control member with a sequential circuit controlling,electrically heated thermal timer in controlling both the operation ofthe timer and the selective energization of an electroresponsive deviceas to meet the essential control and safety requirements encountered inoil burner control or other similar control service.

Another object is to provide an improved form of interlocking and safetycircuit control mechanism for quickly and selectively responding only tothe initial changes in a widely variable temperature condition such asproduced upon initiation and termination of combustion of an oil burner.It is a particular object of my invention to provide such aninterlocking and safety circuit control mechanism which is adaptable foruse with a regulated air bellows form of temperature responsive device.

Further objects and advantages of the invention will become apparentfrom the following description of the accompanying drawing in which Fig.1 is a schematic perspective View of a condition responsive timing andsequencing circuit control embodying the improvements of the presentinvention in a preferred form suitable for oil burner control service,Fig. 2 is a timesequence diagram of the various condition responsive,timing, and sequencing control functions provided by the improvedcontrol and Fig. 3 is a fragmentary view showing schematically therelative positions of the lookout sequence control parts under differentconditions of operation.

As shown schematically in Fig. l, the invention is applied to control anoil burner H] which fill may be of a conventional type operated by anelectric motor indicated by winding H. able oil pumping mechanismenclosed within the pump casing l2 as well as a combustion air blowerwithin the blower casing l3 are both operated when the driving motor I lis energized. As indicated, oil is supplied under pressure through pipeM to atomizing nozzle l5 and combustion air is supplied through conduitl8 and air supply tube H for mixing with the atomized oil to project acombustible mixture into a combustion chamber l8 defined by the-wall l9.Under normal burner operating conditions, this combustible mixture isignited by means of ignition transformer 2i and the high-voltage sparkelectrodes 22. However, under some abnormal conditions, combustion maynot be successfully established during a limited starting period and itthen becomes imperative that further operation of the oil burner bestopped. Otherwise a dangerous explosion might occur due to theaccumulation of a relatively large amount of unburned atomized oil inthe combustion chamber. The present invention provides improved meansfor selectively and positively differentiating in an im'- proved mannerbetween the normal establishment of combustion and the failure toestab-' lish combustion while the motor II is initially energized duringthe limited starting period.

Burner motor H is energized from suitable electric supply lines Ll, L2,preferably under control of an electroresponsive relay 23 having anoperating winding 24 energized from the lowvoltage secondary of atransformer 25. Relay 23 is operated under the control of an improvedtiming and sequencing switch mechanism indicated generally by thereference character 26 which is combined in interlocking relation withan improved combustion responsive device indicated generally by thereference character 21. A master control switch in the form of aconventional room thermostat 28 or the like is provided for initiatingand terminating burner operation to regulate a predetermined conditionsuch as the room temperature.

The timing and sequencing mechanism 26 is provided with a movablethermal timing element 30 having an electric heater 3| supported inheating relation with the thermal element 30 by bracket 32 mounted on aprojection 33 from the base 34. The thermal timin main supportingelement 35 is shown as of the bimetallic type fixed at lower end andcarrying at its upper end contact plate on which switching contacts 36are mounted back to back so as to abut selectively with the cooperatingswitch contacts 31 Switch contact 31 is resiliently carried by a springstrip 48 mounted on the arm 4| which in mounted by the flexible strip ofmagnetic material and is movable into magnetic attractive relation withthe permanent magnet 46 that is carried by the switch plate 35, beingsuitably secured thereto as by screw 45. Thu a releasable holding meansis provided by magnet and arm 4| for maintaining contact 3? in resilientabutment with contact 35 during a predetermined movement of the switchplate 35 by the thermal element 30 due to the heating thereof until arm4| engages the extension 41 of adjustable stop 48 to release arm 4| frommagnet 46. Thus the adjustment of stop 48 by adjusting screw 49regulates the heating period of thermal element 30.

Switch contact 38 is carried by a flexible strip 50 extending from thebase 34 to position contact 33 so as to engage with contact 36 duringthe predetermined heating of the thermal element 35. To eliminatediniculties due to chattering of room thermostat 28, the switch plate 35also may carry contact 5| into abutting engagement with contact 52carried by the flexible strip 53 extending from the base 34 thermostat28 for a limited interval during the starting of burner H).

The combustion responsive device 21 in the improved form shownair-filled bellows 55 mounted on a connection base 55 and interconnectedthrough tube 51 with a temperature bustion chamber l8. An operating arm59 is pivotally mounted on the pin 60 to engage with and be operated bythe finger 6| extending from the closed end of the bellows 55. arm 58 isopcrabl connected with the switching interlock member 52 that is movablymounted by means of bracket 63 and the resilient mounting spring 64extending from a fixed support 65 having a motion limit stop 66.

As explained more in detail hereinafter the interlocking member 62 isprovided with a projecting finger 69 for cooperating with the extension?5 of switch plate 35, an interlocking finger 7| for cooperating withthe bent-over extension 52 of the flexible strip 53 and an adjustablymounted interlocking finger "I3 for cooperating with the extension 14 ofthe movable magnetic arm 4|. Also, interlocking member 62 carries afinger 15 for engaging with arm 16 to separate the normally closedswitch contacts T! and thereby open the primary circuit of the ignitiontransformer 2| after combustion is established.

An improved automatic air pressure control valve mechanism 89 isprovided for regulating the air pressure to which the bellows 55 issubjected both before heating of the bulb 58 in response to combustionand also during the heat- As shown, a conventional form adjusting screw86 into and out of engagement with the tire valve stem 81.

The improved pressure control operates as follows: When the bulb 58 iscooling, bellows 55 contracts due to the decreased internal air pressurebelow atmospheric and a suitable spring 88 moves lever 59 to carry thehead of adjustable screw 89 into engagement with the forked end of thepressure control lever 84 so as to engage adjustable screw 86 with valvestem 87 and thereby open the tire valve 8|. As a result, the airpressure inside of bellow 55 becomes equalized with the outside airpressure and bellows 55 then can expand sufficiently to reclose tirevalve 8|. In this way a predetermined equalized pressure is alwaysprovided inside the bellows 55 when bulb 58 is cooled.

When bulb 58 is heated, the resulting increase of internal air pressurecauses bellows 55 to expand relatively quickly until the knob 90 onlever 59 engages adjusting screw 9| and tilts lever 84 to pressadjusting screw 86 against valve stem 81 to open valve 8| andtherebyrelease some of the increased pressure inside of bellows 55. When thepressure inside bellows 55 is thus released, valve 8| is automaticallyreclosed. In this way, even though bulb 58 is finally heated to arelatively high temperature, the pressure inside of bellows 55 is alwaysprevented from increasing beyond a predetermined maximum value.Consequently, by means of the improved pressure regulating valvemechanism bellows 55 is able to respond relatively quickly to arelatively small increase or decrease of the temperature of bulb 58 toeffect reverse operations of interlocking member 62. This in turnenables a very quick and positive response of bellows 55 to theestablishment or termination of combustion to be obtained.

The combustion responsive device 21 is describe Operation With thevarious parts in their respective positions shown in Fig. 1, the oilburner |0 is started into operation upon closure of the master controlswitch 28. Thi first closes a time delay heating circuit extending fromthe secondary of transformer 25 through relay winding 24, conductor I55,master switch 28, conductor |0|, switch plate 35, abutting contacts 36and 31, strip 45, arm 4|, strip 42, support 43, conductor I52, heater 3|and conductors I03 and H14 to the opposite terminals of the transformerwinding. Due to the current limiting action of electric heater 3|, theresulting limited energization of relay winding 24 is below the pick-upvalue and hence is ineffective to cause response to the relay to closecontact 23. However, heater 3| begins to heat thermal timing element 30to produce movement of the upper end thereof to the left as indicated bythe arrow I-I. Magnet 46 holds plate 4| in attractive relation therewithso as to maintain contacts 36, 31 n abutment during a predeterminedheating period of element. As' ndi a ed in F 2, th s h ati g er od etends from the initial starting time To when master switch 28 closes itscontacts to time T2 when contact 31 becomes separated'from contact 36due to engagement of arm M with the extension 4'! of the adjustable stop48. During this heating period, thermal element 30 carries plate 35 toabut contact 36 with contact 38 at a time indicated in Fig. 2 as Tl.Thus during a relatively short interval between time TI and time T2contact 36 is maintained in abutment with both contacts 31 and 38. 1

' Upon abutment of contact 36 with contact 33 at time TI a parallelcircuit is closed shunting the electric heater 3|. This parallel circuitextends from contact 36 through contact 38, strip 50, and a suitablecurrent limiting resistor i 35. With resistor Hi thus connected inparallel or shunt with the electric heater 3 i, the relay winding 24 nowbecomes sufficiently energized to pick up and eflect operation of relaycontact 23 from its normally opened position in which it is shown to theclosed position to start operation of burner Hi.

Upon closure of relay 23 the oil burner operating motor H is energizedfrom supply line Ll. through conductor Hi1, relay 23, conductor tilt,the energizing winding of motor ll and conductor I09 and the usualsafety limit switches lie. Also, the closure of relay 23 energizes theigni tion transformer 2!, the circuit extending through conductor Hi,normally closed ignition control switch contacts ll, conductor H2, theprimary ignition transformer 2i, and conductors H3 and i539 and limitswitch till. With both motor H and ignition transformer it thusenergized upon closure oi relay 23 at time Tl in the diagram of Fig. 2,the subsequent operation oi. oil burner iii should successfullyestablish combustion within a limited time thereafter. During thislimited time contacts 5! and 52 bypass the master switch 23 to insureagainst the difficulties that might result from chattering of the roomthermostat contacts.

Let us assume that combustion is initially established at time E, asshown in diagram of Fig. 2, during the cooling period of thermal element38. At this time relay 23 is maintained effectively energized entirelyby the shunt circuit including resistor I95 since thermal element 3!!had previously moved contact plate 35 in the direction of the arrowsuiiiciently to pull arm 4|, through the agency of magnet 4%, intoengagement with adjustable stop 4'! and thereby release the arm from themagnetic attraction of magnet .6. Thereupon arm M and strip 49 arebiased by resilient strip 22 to move to the right until extension I lengages with the sloping cam surface lfia of the adjustably mounted cam33 so as to carry arm 6! entirely out of attractive relation with magnet46 and contact 31 out of abutment with contact 36 and thereby open thecircuit through electric heater 3i and thus terminate the heating periodand initiate the cooling period of thermal element 39 at time T2.

With combustion established at time E as assumed, the bulb 58 willquickly become heated to expand bellows 5-5 and thereby relativelyquickly operate interlocking member 62 upwardly so as to move arm ll tothe left due to carnming action of the sloping surface 13a on extensionit and thus return arm ll into the position indicated by the dottedlines in Fig. 3 to be attracted by magnet All when the latter returns-toitsnormal starting position as shown in Fig. 3. The further upwardmovement of member 63 also will position finger 69 in the path ofextension ill, finger H in the path of the projection l2 and engagefinger T5 with the arm it to separate contact 11 and thereby deenergizethe ignition transformer 21. Thus as thermal element 30 continues tocool, finger ll engages with extension 12 to separate contacts 5|, 52and thereby remove the by-pass circuit around the master controlthermostat 28. Shortly thereafter, projection I0 engages the finger 59so as to block further movement of plate 35 to the right even thoughthermal element as continues to cool. Consequently, contact 3% ismaintained in abutment with contact 38 by the blocking engagement offinger 69 with extension in in response to establishment and maintenanceof combustion during the cooling period or thermal element 30.

Under assumed conditions, when combustion is once successfullyestablished and maintained during the cooling period of thermal element38, the burner motor ii is thereafter operated under the joint controlof the combustion responsive device 2?, master control switch 2b andrelay 23. Thus, in case for any reason combustion should fail after timeT3, the improved control insures an automatic restart of the burner inthe following manner: Upon the initial cooling of bulb 58 bellows berelatively quickly responds to move interlocking member 62 downwardlyand thus disengage finger its from extension 1!) and thereby free plate35 for snapaction movement contact 3"! due to the resilient biasingaction provided by the cooling of thermal element 30.

Such reengagement of contacts 3% and 31 after termination of combustionis obtained solely due to the {act that when finger B9 disengagesextension it to release plate 35 for snap action movement, the camsurface 53a of interlocking finger is still engages extension it of armil as indicated by the dotted lines in Fig. 3 and thus holds arm t! in aposition to again be at tracted and thereby held by magnet 56 andconsequently maintain contact 3i in engagement with contact 36. Upon therelease of plate 35, contact 36 disen'gages contact 38 and thereby opensthe maintaining circuit through resistor for relay 23. As a result relay23 returns to its open position and deenergizes burner motor H.

Upon the snap action reengagement oi contacts 36 and 31 just described,the electric heater 3! again is energized and thermal element 36 againis heated to restart burner operation in precisely the same timed cycleas described above. Furthermore, exactly the same automatic restartoperation is obtained in case of voltage failure of the power supplylines Li, L2, wheneverthe power failure is of sumcient duration toproduce a. response or the combustion responsive device 2? to slow downor stop the burner operation and thereby cool bulb 53.

In case a normal burner operation has con-- tinued sufficiently tosatisfy the demands of the master control thermostat 28, the opening ofthe thermostat contacts will deenergize relay 23 and thus stop furtherburner operation at time Trc shown in Fig. 2. In this case, contact 36is returned into engagement with contact 31 and magnetite intoattractive relation with arm M in exactly the same manner as previously.de-

scribed. Thus the improved control is ready to to reengage contact 38with V restart the burner whenever the master switch 28 again reclosesits contacts.

Let us now assume that due to some fault of the burner it, combustion isnot successfully established during the cooling time or" thermal element36. In this case interlocking member 62 will remain in its initialposition during the entire starting cycle time since bulb 58 is notheated and bellows 55 is not expanded. Hence, the adjustable interlockstop 73 is maintained in its initial lockout position shown in fulllines in Fig. 3 to engage with extension H without exerting any cummingaction thereon that would tend to return arm il into attractive relationwith magnet 43. Consequently arm 4! when released at time T2 moves inaccordance with its bias provided by resilient strip 2 as adjusted byscrew 4 to a lookout position that is out of attractive relation withmagnet 4G when thermal element 39 has cooled as shown by the dot-dashlines of Fig. 3. Thus, when element 39 has cooled extension is willengage with the flat end of interlocking member 52 but arm 43! will notbe magnetically attracted or held by magnet 15 and thus contact 37 willnot abut contact 36. In this way the improved control is automati callylocked out when combustion is not successfully established by apredetermined time L that is before the end of the cooling time T3.

T0 restart burner operation after such an automatic lock-out and afterthe burner fault producin the look-out has been corrected, the manualpush-button H5 is operated to engage the extension H6 with arm 45 tomove this arm into magnetic attractive relation with magnet 46. At thesame time extension iii engages with strip to so as to move contact outof the range of movement of contact 35. Only a momentary operation ofthe reset button H5 is required since arm 4| will at once be held bymagnet es and pushbutton it 5 may then be returned to its initialposition by spring H8 to restore the whole control again to its normaloperating condition.

t will be understood that in case a non-chattering type of roomthermostat 28 is employed, then the thermostat automatic shuntingcontact control comprising the contacts 5!, 52 may be omitted ifdesired. Likewise, in case deenergization of the burner ignition systemis not desired after combustion is established, the ignition controlswitch 7? also may be omitted. Furthermore, while the preferred form ofair pressure responsive bellows combustion responsive mechanism has beendisclosed for operating the interlocking control member 62, it will beunderstood that this control 52 may, if desired, be operated by anyother suitable forms of combustion responsive devices such, for example,as a conventional expansible tube and rod or the like.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A condition responsive timing and sequence control having incombination circuit control means including a switch for closing acircuit, means for closing said switch upon termination of apredetermined condition including a condition responsive device, athermal timing element having an electric heater in said circuit foropening said switch upon a redetermined heating of said element, andinterlocking connections b tween said device and said element formaintaining said switch op n upon non-response of said device to saidcondition during cooling of said element.

2. An electrically operated burner control having in combination burnerstarting means including a switch for closing a circuit essential forburner operation, means for closing said switch upon termination ofoperation of the burner including a combustion responsive device and athermal timing element having an electric heater in said circuit, meansfor opening said switch after a predetermined heating of said element,and means interlocking said combustion responsive device and saidthermal timing ele: ment for maintaining said switch open to lock outsaid burner starting means upon non-response of said device tocombustion during cooling of said element.

3. An electrically operated burner control havin in combination burnerstartin means including a switch for closing a circuit essential forburner operation, means for closing said switch after a heating cycleoperation of the burner establishing combustion including a, combustionresponsive device and a thermal timing element having an electric heaterin said circuit, interlocking connections between said device and saidelement for opening said switch upon a predetermined heating of saidelement and for maintaining said switch open to lock out said burnerstarting means upon non-r spouse of said device to combustion duringcooling of said element, and manually Operable means for reclosing saidwitch to restart burner operation.

A condition responseve timing and sequence control having in combinationcontrol means ineluding abutting contacts for closing a circuit, meansbiasing one or" said contacts to open said circuit, timing meansincluding a reversely movable thermal timing element carrying the otherof said contacts and having an electric heater in said circuit andprovided with releasable magnetic holding means for maintaining said onecontact in abutment with said other contact until after a predeterminedheating of said element, and sequencing mean including a conditionresponsive device and cam operated interlocking means responsive theretofo controlling said one contact to maintain said contacts out ofabutment upon non-response of said device to a predetermined conditionduring cooling of said element and for abutting said contacts upontermination of said condition after cooling of said element.

5. A condition responsive timing and sequence ci'cuit control systemhaving in combination a first circuit having abutting contacts forclosing said circuit, timing means including a reversely movable thermaltiming element carrying one of said contacts and having an electricheater in said first circuit and provided with releasable means formaintaining the other of said contacts in circuit closing abutment withsaid one contact until after a predetermined heating of said element, acondition responsive device having connections for controllin the otherof said contacts to maintain said contacts out of abutment uponnon-response of said device to a predetermined condition during coolingof said element, a second circuit having abutting contacts for closingsaid second circuit, one carried by said element into circuit closingabutment with the other upon said predetermined heating of said elementand interlocking means operated by said condition responsive device formaintaining said second circuit controlling contacts in abutment inresponse to occurrence of said condition during said cooling of saidelement and for main taining said first circuit closing contacts out ofabutment until termination of said condition.

6. A condition responsive timing and sequence control having incombination electroresponsive condition control means having energizinmeans including a circuit and a switch for closing and opening saidcircuit, means for closing said switch including a condition responsivedevice and a thermal timing element having an electric heater in saidcircuit, and means interconnecting said condition responsive device andsaid thermal timing element for opening said switch after apredetermined heating of said element and for maintaining said switchopen upon non-response of said device to a predetermined conditionduring cooling of said element.

7. A condition responsive timing and sequence control having incombination a circuit including an electric heater and a switch forclosing and opening said circuit, electroresponsive means dependent uponclosure of said circuit for establishing a predetermined condition andhaving a maintaining circuit, means for closing said switch including acondition responsive device responsive to said condition and a thermaltiming element heated by said heater, and interconnecting means betweensaid condition responsive device and said thermal timing element forcontrolling said maintaining circuit upon establishment of saidcondition and having correlated connections for opening said switchagain after a predetermined heating of said element and for maintainingsaid switch open until termination of said condition after cooling ofsaid element or upon non-establishment of said condition during coolingof said element.

8. A condition responsive timing and sequence control having incombination circuit control means including an elongated reverselymovable thermally responsive timing element having an electric heaterand having switching means for sequentially closing one circuit andopening another circuit including said heater during a heating intervaland for sequentially opening said one circuit and reclosing said othercircuit during .a cooling interval, means including an electroresponsivedevice for normally establishing a condition during closure of both saidcircuits and maintaining said condition established upon continuedclosure of said one circuit, and a condition responsive device havingcam interlocking means associated with said timing element forcontrolling said switching means to maintain said one circuit closedupon establishment of said condition before the end of said coolinginterval and for preventing reclosing of said heating circuit uponcooling of said element only after failure to establish said conditionbefore the end of said cooling interval.

9. A condition responsive timing and sequence control having incombination means including an electroresponsive device for normallyestablishing and maintainin a condition during effective energization ofsaid device, circuit means including parallel circuits for effectivelyenergizing said device only upon closure of both said circuits and thesimultaneous passage of current through both circuits of said device andupon subsequent continued closure of one of said circuits, means forclosing the other or said circuits including an electrical timeroperable responsively to said closure or" the other of said circuits andhaving a first switching means for maintaining said other circuit closedonly forfan interval and a second switching means for closing said onecircuit before the end of said interval to effectively energize saidelectroresponsive device, and means including a condition responsivedevice having one interlocking means for maintain-' ing said secondswitching means closed to maintain said device effectively energizedupon establishment of said condition before the end of a second intervaland another interlocking means for maintaining said first switchingmeans ineffective to reclose said other circuit after failure toestablish said condition before the end of said second interval.

10. A condition control system having in com bination a first switch, athermal timing operating element for closing said switch during heatingof said element and opening said witch during cooling of said element, acondition responsive device having interlock means for maintainin saidfirst switch closed during the occurrence of a predetermined condition,a second switch having correlated operating means including saidcondition responsive device and said thermal ele: ment for closing saidsecond switch only after opening said first switch upon the terminationof said predetermined condition and maintaining said second switch openafter the non-occurrence of said condition, said thermal element havingreleasable holding means for maintaining said second switch closed foran interval after said closing of said first switch during said heatingof said element, an electric circuit under control of said second switchand including in series a master switch an electric heater for saidthermal element and an electroresponsive device having means forcontrolling said condition, and a resistor for shunting said heater uponclosure of all said switches to effectively energize said electroresponsive control device to establish said condition and maintain saiddevice efiectively energized to maintain said condition under jointcontrol of said master switch and said first switch upon opening of saidsecond switch.

11. A condition responsive timing and sequencing control mechanismhaving in combination three movable switch members having contacts forselectively controlling two parallel circuits. a master switch forcontrolling the closure of said circuits by said switch members, timedelay operating means for one of switch members including a reverselymovable thermally responsive operating element having an electric heaterenergized under control of said master switch upon closure of one ofsaid circuits for heating said element to operate said one switch memberwith a time delay after closure of said one circuit and to contact asecond of said switch members to close the other of said circuits,releasable means under control of said operating element for maintainingthe third of said switch members in contact with said one switch memberto maintain said one circuit closed until the end of a limited heatinginterval for said operating element after said other circuit is closed,and condition responsive means having a movable interlocking memher forcooperating upon the occurrence of a predetermined condition before theend of a secone. interval beginning at the termination of said firstinterval with said operating element to maintain said one and said otherswitch members in contact upon cooling of said operating element,

and means under joint control of said condition responsive means andsaid operating element for controlling the reestablishment of tween saidone switch switch member after cooling contact bemernber and-said thirdof saidel'ement and dependent upon the occurrence or absence of saidcondition before the end of said second interval.

12. A variable temperature responsive timing and sequence control havingin combination control means including abutting contacts for closing acircuit, means biasing one of said contacts ing the other of saidcontacts and having an electric heater in said circuit and provided withrecontact until after a predetermined heating of said element, andsequence control means including an initial reverse temperature changeresponsive device and cam interlocking means for con trolling said onecontact to maintain said contacts out of abutment upon non-response ofsaid device to a predetermined initial reverse tem perature changeduring cooling of said element and for reabuttins, said contacts onlyupon occurrence of an opposite initial reverse temperature change aftercooling of said element.

13. A temperature change responsive timing and sequencing control,having in combination electroresponsive temperature control means havingenergizing means including a circuit and a switch for closing andopening said circuit, means for closing said switch includng atemperature 12 change responsive device and a thermal timing elementhaving an electric heater in said circuit and having correlatedconnections including a magnet carried by said element for holding saidswitch closed and a stop positioned to engage said switch for openingsaid switch after a predetermined heating of said element and meansincluding a movable stop member positioned by said taining said switchopen upon non-response of said device to a predetermined temperaturechange during cooling of said element.

ALBERT WELL-MAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

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